Field of Invention
The present technology generally relates to oriented polymer composite (OPC) material and solid state draw dies used in conjunction with the manufacture of the OPC material.
Description of Related Art
Oriented polymer composite (OPC) articles can be formed by solid state die drawing process in conjunction with solid state extrusion process. To form an OPC article, a polymer composition is typically first pushed through an extruder using ram extrusion or hydrostatic extrusion processes. The extruded polymer billet is then pulled through a solid state draw die. The solid state draw die reduces the cross-sectional area of the polymer billet and causes it to converge toward the desired profile, thereby forming the OPC article.
Conventional wisdom appears to dictate that axisymmetric deformation and proportional draw dies are necessary to produce a dimensionally accurate OPC product. For example, U.S. Pat. No. 7,687,002 to Nichols et al. discloses the importance of using a substantially proportional draw die for balanced drawing of polymer compositions into shapes having non-circular cross sections. According to the '002 patent, substantially balanced drawing results from a drawing path where any polymer composition cross section is substantially proportional to any other polymer composition cross section and where the centroid of any polymer composition cross section lies on a substantially straight line that is parallel to the drawing direction. The '002 patent discloses that substantially balanced drawing offers a benefit of maintaining substantially proportional polymer cross sections despite changes in draw rate. The '002 patent further discloses that a substantially proportional die achieves streamline flow of a solid state polymer through the die while maintaining a final article cross section that is substantially proportional to a polymer composition draw channel cross section.
Efforts to produce dimensionally accurate OPC products appear to have been largely focused on proportional draw dies to effect axisymmetric deformation and streamlined flow. While proportional draw dies may be effective for simple symmetric profiles such as tubes and rods, they may not be adequate for producing dimensionally accurate complex asymmetric OPC profiles. Accordingly, there is still a need for an improved draw die and related process for producing complex asymmetric OPC profiles.